Since 2019.3 is still in beta, I was curious to know if it was possible to use URP within 2019.2.8.?
As it’s a package, is should be possible to copy the package and directly use it in unity 2019.2.8, but does it require some dependencies of unity 2019.3?
LWRP renamed as URP is only available for 2019.3 as it’s been stated in the blog etc. If you want to (for some reason) try to hack something, you probably have to do it yourself. 
It’s unfortunately not only renamed, a lot of functions have been added and or deprecated, we’re porting our game from Build-In to URP and have a functional version on unity 2019.3.
However, The editor of Unity 2019.3 is quite unstable and the physic changes bring too many risks at the moment in our project. That’s why I’m asking
Are there any concrete issues you’re experiencing with 2019.3? Could you please specify what doesn’t work for you?
The Universal RP package is not compatible with versions prior to 2019.3.
https://blogs.unity3d.com/2019/09/20/how-the-lightweight-render-pipeline-is-evolving/
We had lots of random crash of the editor itself, but not related to URP.
the crashes usually don’t even prompt the bug report window, it’s like suddenly unity disappear… I’m sorry I can’t tell you more than that 
What physics risks? The main risk is that a second trigger event may be fired upon kinematic reinsertion but thats easy to catch and ignore. Other than that it basically functions the same but is far faster.
As for the editor instability, I am not seeing anything more unstable than current version of 2019.2. Are you using 3rd party assets? We dont use any and have no issues so that could be the root cause.
I am pretty sure you will be fine on 2019.3 as long as you have a decent source control system in place - which should be a given for any project version.
Either way, please file bug reports if your getting crashes, just mentioning it crashes isnt really helpful to the unity team.